What type of vehicle is it in and have you updated the esc and change the firmware to the right type of model i.e. 1/10 buggy normally uses modify 2.
After this setup your transmitter again to the esc
Check pinion and spur ratios and make sure its not tight so it has too much resistance when turning, check motor isnt tight to turn by hand also.
What turn motor you using ?
Could be a duff speedo too.
I know the pro comes with mod1 installed not normally a match for buggys as its more for touring cars i believe.
Put a picture up of your wiring maybe, its normally the most obvious you fail to spot
